Curcumin (Diferuloylmethane), a polyphenolic compound with antioxidant, anti-inflammatory and anticancer properties, has been found to increase chemotherapeutic agents-induced cytotoxicity in some resistant cancer cell lines. This investigation aimed to study the effects of curcumin on efficacy of some common anticancer agents in gastric cancer cells. AGS cells were cultured in RPMI-1640 medium under standard culture conditions (5% CO2 and 95% humidified air at 37°C). Curcumin was used at concentrations of 5, 15, 30 and 50 μM. Cells were treated with a combination of curcumin and paclitaxel (300 nm) or methotrexate (100 μm) or vincristine (5 nm). Cell viability, the percentage of live cells in the whole population, was evaluated by MTT assay after 48 hours. The results showed that cell viability was significantly decreased after incubation of AGS cells with curcumin. Combination with curcumin (15-50 μm) significantly increased cytotoxicity of all three agents (P<0.001). Regarding high anticancer potential and enhancement of chemotherapeutic agent-induced cytotoxicity, the combined use of curcumin with standard chemotherapy of gastric cancer is suggested as a strategy for better management of this fatal cancer.